The last of the four major storm types is
the supercell. We define a supercell as a
thunderstorm with a deep rotating updraft (mesocyclone).
In fact, the major difference between supercell
and multicell storms is the element of rotation
in supercells.
As we shall see, circumstances keep some supercells
from producing tornadoes, even with the presence of
a mesocyclone.

Even though it is the
rarest of storm types, the supercell is the most
dangerous because of the extreme weather generated.
This storm was producing baseball hail east of
Carnegie, Oklahoma, as it was photographed looking
east from 30 miles. From right to left (south to
north), we note the flanking line, main
Cb, and
downwind anvil above the precipitation area.

The
flanking line of the supercell behaves differently
than that of the multicell cluster storm, in that
updraft elements usually merge into the main rotating
updraft and then explode vertically, rather than develop
into separate and competing thunderstorm cells.
In effect, the flanking updrafts "feed" the supercell
updraft, rather than compete with it.